Question

What is the general form of the equation of a circle with a center at the (4, 2) and a radius of 9?

Answer 1

so, what's the equation for a circle, from your formulas sheet?

Answer 2

(x -h)^2 + (y - k)^2 =r^2?

Answer 3

The general equation for a circle is
\[(x-h)^2+(y-k)^2=r^2\]
h is the transformation going on the x axis, and k is the transformation on the y axis.

Answer 4

well, then just PLUG IN the values :), what you were given is (h,k)

Answer 5

and "r" too, so, you have everything :)

Answer 6

oooh lol makes sense thank you :)

Answer 7

So, to move a circle to the right, or positive x direction h must be negative.
And to move a circle up, or positive y direction, k must be negative.

Answer 8

oh ok I get it now ty :)

Answer 9

So we are moving the circle right 4 and up 2, both positive. So, what does that make our formula?

Answer 10

is it (x – 4)^2 + (y – 2)^2 = 81?

Answer 11

It is indeed! Good Job!

Answer 12

awesome thanks so much :)

Answer 13

No problem!